Abstract
Irrigation can affect climate and weather patterns from regional to global scales through the alteration of surface water and energy balances. Here, we couple a land-surface model (LSM) that includes various human land-water management activities including irrigation with an atmospheric general circulation model (AGCM) to examine the impacts of irrigation-induced land disturbance on the subseasonal predictability of near-surface variables. Results indicate that the simulated global irrigation and groundwater withdrawals (circa 2000) are ~3600 and ~370 km3/year, respectively, which are in good agreement with previous estimates from country statistics and offline–LSMs. Subseasonal predictions for boreal summers during the 1986–1995 period suggest that the spread among ensemble simulations of air temperature can be substantially reduced by using realistic land initializations considering irrigation-induced changes in soil moisture. Additionally, it is found that the subseasonal forecast skill for near-surface temperature and sea level pressure significantly improves when human-induced land disturbance is accounted for in the AGCM. These results underscore the need to incorporate irrigation into weather forecast models, such as the global forecast system.
Highlights
Interactions between land and atmosphere are important drivers of the Earth’s climate and weather systems [1,2]
We note that the objective of this evaluation is not to provide an extensive validation of the model results but, rather, to ensure that the results from the atmospheric general circulation model (AGCM)–Human setting—which has different climatology of precipitation and temperature—do not depart significantly from the offline model results due to climatological bias and are in general agreement with the reported statistics
We focus on the spatial patters of long-term mean irrigation water use and groundwater withdrawal and their total global volumes
Summary
Interactions between land and atmosphere are important drivers of the Earth’s climate and weather systems [1,2]. Agricultural land management and irrigation are by far the most important anthropogenic factors that affect land-surface conditions and the terrestrial water cycle These anthropogenic factors can alter the biophysical properties of the land surface, such as its albedo, roughness, leaf area index, and rooting depth, affecting various hydroclimatic processes, such as evaporation from land, transpiration from leaf stomata, and regional precipitation patterns [7,8,9,10,11].
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